School of Pharmacy and Pharmaceutical Sciences, The University of Manchester, Manchester, UK.
Mol Cancer. 2010 Feb 15;9:38. doi: 10.1186/1476-4598-9-38.
The cyclin-dependent kinase (CDK) and mitogen-activated protein kinase (MAPK) mediated phosphorylation of glucocorticoid receptor (GR) exerts opposite effects on GR transcriptional activity and affects other posttranslational modifications within this protein. The major phosphorylation site of human GR targeted by MAPK family is the serine 226 and multiple kinase complexes phosphorylate receptor at the serine 211 residue. We hypothesize that GR posttranslational modifications are involved in the determination of the cellular fate in human lymphoblastic leukemia cells. We investigated whether UV signalling through alternative GR phosphorylation determined the cell type specificity of glucocorticoids (GCs) mediated apoptosis.
We have identified putative Glucocorticoid Response Elements (GREs) within the promoter regulatory regions of the Bcl-2 family members NOXA and Mcl-1 indicating that they are direct GR transcriptional targets. These genes were differentially regulated in CEM-C7-14, CEM-C1-15 and A549 cells by glucocorticoids and JNK pathway. In addition, our results revealed that the S211 phosphorylation was dominant in CEM-C7-14, whereas the opposite was the case in CEM-C1-15 where prevalence of S226 GR phosphorylation was observed. Furthermore, multiple GR isoforms with cell line specific patterns were identified in CEM-C7-14 cells compared to CEM-C1-15 and A549 cell lines with the same antibodies.
GR phosphorylation status kinetics, and site specificity as well as isoform variability differ in CEM-C7-14, CEM-C1-15, and A549 cells. The positive or negative response to GCs induced apoptosis in these cell lines is a consequence of the variable equilibrium of NOXA and Mcl-1 gene expression potentially mediated by alternatively phosphorylated GR, as well as the balance of MAPK/CDK pathways controlling GR phosphorylation pattern. Our results provide molecular base and valuable knowledge for improving the GC based therapies of leukaemia.
细胞周期蛋白依赖性激酶（CDK）和丝裂原活化蛋白激酶（MAPK）介导的糖皮质激素受体（GR）磷酸化对 GR 转录活性产生相反的影响，并影响该蛋白内的其他翻译后修饰。MAPK 家族靶向的人 GR 的主要磷酸化位点是丝氨酸 226，多个激酶复合物在丝氨酸 211 残基上磷酸化受体。我们假设 GR 的翻译后修饰参与决定人淋巴母细胞白血病细胞的细胞命运。我们研究了通过替代 GR 磷酸化的 UV 信号是否决定了糖皮质激素（GCs）介导的细胞凋亡的细胞类型特异性。
我们在 Bcl-2 家族成员 NOXA 和 Mcl-1 的启动子调控区域内鉴定出了推定的糖皮质激素反应元件（GRE），表明它们是直接的 GR 转录靶标。这些基因在 CEM-C7-14、CEM-C1-15 和 A549 细胞中被糖皮质激素和 JNK 途径差异调控。此外，我们的结果表明，S211 磷酸化在 CEM-C7-14 中占优势，而在 CEM-C1-15 中则相反，S226 GR 磷酸化占主导地位。此外，与 CEM-C1-15 和 A549 细胞系相比，在 CEM-C7-14 细胞中鉴定出具有细胞系特异性模式的多种 GR 同工型。
CEM-C7-14、CEM-C1-15 和 A549 细胞中 GR 的磷酸化状态动力学、特异性和同工型变异性不同。这些细胞系对 GCs 诱导的细胞凋亡的阳性或阴性反应是潜在由不同磷酸化的 GR 介导的 NOXA 和 Mcl-1 基因表达的可变平衡的结果，以及控制 GR 磷酸化模式的 MAPK/CDK 途径的平衡。我们的结果为改善白血病的 GC 治疗提供了分子基础和有价值的知识。
